1. Field of the Invention
The present invention relates to ophthalmic surgery, and particularly to an intraocular lens fixation device that provides precise, accurate alignment of an intraocular lens with minimal risk during the ophthalmic surgical procedure.
2. Description of the Related Art
An intraocular lens (IOL) is a synthetic lens used to correct various eye-related impairments, such as cataracts, astigmatism, and refractive errors. The impaired crystalline lens in the eye is replaced by the IOL through implant surgery. IOLs have been very effective in correcting vision, but the implant procedure is a precise, delicate and risky surgery that, if not performed correctly, can lead to potential infection, loosening of the lens, lens rotation, inflammation, nighttime halos, and some loss to potential vision.
Many different types of IOLs are available. Each type is specifically designed to correct a certain type of eye defect or vision impairment, e.g., multifocal IOLs for simultaneous viewing of both long and near distances, and accommodating IOLs for both long and midrange near distance vision. Another type of IOL is a tonic IOL. The tonic IOL has been recently introduced to correct astigmatism in patients undergoing cataract surgery. With accurate IOL calculations and surgical technique, tonic IOLs can minimize or eliminate the need for spectacles following cataract surgery. It has been estimated that about 15-20% of patients with cataracts have astigmatism and will benefit from this lens.
To maximize the benefits of these premium lenses, accurate positioning or alignment is extremely important. The accuracy of new diagnostic tools, such as Lens Star® or IOL Master®, has contributed to the success of these lenses. When incorrectly placed, however, post-operative vision accuracy will be compromised, depending upon the degree of misalignment. For example, 15° off-axis will result in a 33% vision drop, which is not infrequent. Several studies have shown that a difference of about 10-30° of misalignment between the targeted and the achieved axis was seen in about 30-60% of the cases. Some of these cases showed a misalignment of about 45° or more. An acceptable misalignment of 5° or less was only seen in about 40% of cases. Most of these errors can be attributed to human error.
Diagnostic instruments measuring IOL power and astigmatism, such as IOL Master® or Lens Star®, are very accurate and reproducible. The discrepancy between the targeted and the achieved axis is due to identification of the proper axis, preoperative markings, and/or intra-operative misalignment. Preoperative marking of the cylinder axis is associated with significant human error. In practice, most surgeons do not have the patient in a sitting position to perform accurate axis markings. The markings are usually performed in the operating room in a semi-sitting position. With cyclotorsion, the chance of marking the axis accurately is minimal. In addition, most surgeons use methylene blue ink, which may fade by the time the patient is prepared for surgery, or the ink dilutes widely over 5-10°, which is another potential risk for error.
Intraoperative axis misalignment is mostly seen with inexperienced surgeons, which fortunately improves over time. However, chances of misalignment still exist. Due to manual rotation of the tonic IOL, centering of the IOL is not always accurate. This can cause post-op lens rotation that may lead to misalignment. Another cause of surgical error with IOL rotation is when the visco-elastic is not completely removed during surgery. This will result in clockwise rotation of the IOL. In addition to improper axis alignment, manual rotation of the tonic IOL imposes risks of capsule rupture or zonular damage in cases with weak capsule.
The current microsurgical instruments being used in this type of surgery do not appear to reduce the risks of misalignment. Most typical instruments are a type of forceps that can grab an edge of the IOL for manual rotation of the IOL. This is prone to human error, as mentioned above, with the attendant risk of capsular rupture.
In light of the above, it would be a benefit in the art of ophthalmic surgery to provide a device that can provide precise, accurate alignment of IOL with minimal risk to surrounding tissue during surgery. Thus, an intraocular lens fixation device solving the aforementioned problems is desired.